Broad, Long-Term Objective. To make a significant impact in the clinical management of PAD patients with intermittent claudication by determining whether home-based exercise can be used to treat symptomatology. Rationale. In contrast to supervised exercise programs, home-based exercise for PAD patients with intermittent claudication is poorly understood due to serious flaws in the research approach of previous trials. Specific Aims. (1) This trial will compare the changes in ambulatory function, vascular function, and health- related quality of life in PAD patients limited by intermittent claudication following a home-based exercise rehabilitation program, a supervised exercise program, and an attention-control group who perform light resistance training exercise, and (2) to determine whether changes in walking economy, calf muscle circulation, and calf muscle oxygenation are the major physiologic mechanisms by which both home-based and supervised exercise rehabilitation improve ambulatory function. Research Design and Methods. A prospective, randomized controlled clinical trial will compare a home-based exercise group (N = 37), a supervised exercise group (N = 37), and an attention-control group (N = 37). The two exercise programs will be matched on the estimated caloric expenditure during the training sessions. The 3-month supervised program will consist of graded treadmill walking 3 times per week, and the 3-month home-based program will consist of community-based walking 3 times per week. Walking duration will be longer for the home-based group because the intensity of walking will be lower than the supervised group. Matching on volume of exercise will be done using new technology (step activity monitor) to accurately record community-based ambulation on a minute-to-minute basis for up to a month, and then titrating the caloric expenditure against cadence for each patient during the home-based training sessions. Patients in the attention-control group will perform light-resistance training without any walking exercise. Clinical Significance. This randomized controlled clinical trial will support the notion that home-based exercise can be used to treat PAD patients with intermittent claudication, and will be generalizable to the vast majority of patients who do not have access to a supervised exercise program, but who can benefit from a home-based walking program with minimal intervention from clinicians and minimal use of resources.